This invention relates to sealless joints or splices in strap made of relatively stiff sheet material, i.e., metal strap and the like.
It is known to provide sealless connections between strap ends in the form of an array of longitudinally spaced joints. A very common form of such a joint utilizes a central tongue provided with lateral wing extensions partly along the opposite edges of the tongue. However, the load handling strength of such a connection is reduced because the width of the wing extensions reduces the effective cross section of the strap.
Variations of the aforementioned double wing tongue joint have been suggested over the years. Representative prior art patents in this particular field of art are U.S. Pat. No. 180,910 to Olmsted, U.S. Pat. No. 1,606,331 to Anderson, U.S. Pat. Nos. 2,268,339 and 2,276,988 to Leslie, U.S. Pat. No. 3,137,047 to Mosey, U.S. Pat. No. 3,177,538 to Timmerbeil, and U.S. Pat. No. 3,188,706 to Partridge. Yet in all of the foregoing variations, the effective cross-sectional area of the strap is considerably reduced at the connection, thereby reducing the tensile strength of the connected strap. A sealless connection wherein a relatively higher strength at the connection is realized and lateral pull out action is avoided or minimized is taught in U.S. Pat. No. 3,303,541 to Beach.
In all but one of the aforesaid instances the connection is maintained only while the joined overlapping ends are kept under tension. When tension is temporarily released on the connection, or when the overlapping strap ends are longitudinally shifted relative to each other as someone bumps against the strap connections formed around a temporarily compressed bundle of material which is in the process of being strapped, i.e., a bale of cotton or the like, the connections will release and the joined strap ends will again separate.
In the aforementioned U.S. Pat. No. 3,188,706 to Partridge there is disclosed a means to lock a produced one way tension connection by embossing internested dimples in the overlapped connected strap segments. However, a special tool is required for this purpose, thus the proposed locking means is cumbersome to use. Where a large number of workers performs strapping operations at about the same time, a sizeable investment in special tools must be made. Moreover, unless the embossing is done with care, camming surfaces are formed around the periphery of the embossments which camming surfaces tend to spread the internested dimples apart when the strap segments are subjected to a lengthwise force, i.e., by dropping or subsequent compression of a tied bundle. This action by the camming surfaces will tend to defeat the desired locking action when the lengthwise force is a compressive force, and may promote tearing of the interlocking joints in instances where the connected strap is overtensioned. The fastenerless splice of U.S. Pat. No. 3,188,706 also is cumbersome to form because a two-step operation is needed, i.e., the joints must first be made to interlock and then the internested dimples have to be formed.
The present invention, on the other hand, contemplates a sealless strap connection having an integral locking means which obviates the aforementioned drawbacks and which does not require any tools for affixation.